Influence of Erosive and Abrasive Challenges on mTBS of Adhesives

Objective: The aim of the present study was to evaluate the effect of erosion/ abrasion challenges on microtensile bond strength (mTBS) of a one-step self-etch adhesive (Xeno V) and a two-step one-step self-etch adhesive (Futurabond NR) in vitro. Methods: The study was carried out on ninety extracted third molars. In all teeth cervical dentinal cavities were prepared also allowing the simulation of dentin perfusion. The specimens were randomly assigned to one of the five challenges of thirty samples each: G-1: control; G-2: 5-minute immersion 6x/day in citric acid for 10 days; G-3: G2 followed by tooth brushing abrasion for 1 minute after the first and sixth erosive challenge. Between the erosive/ abrasive challenges, the specimens were immersed in artificial saliva. Subsequently, the dentin specimens were restored with either Futurabond NR/Grandio (F) or XENO V/Grandio (X) or. Microtensile bond strength was measured 15 minutes after application of the composite using an universal testing machine. Results: Following mTBS were evaluated (in MPa): G1-X: 20.06 (+/-3.25); G2-X: 9.36 (+/- 1.90), G3-X: 10.50 (+/-1.80), G1-F:  19.68 (+/-6.22); G2-F: 8.93 (+/-2.90); G3-F: 10.63 (+/-2.24). Statistical analysis showed a significant influence of the used adhesive and the challenge on mTBS (p<0.001, ANOVA). Erosive challenges as well as erosion and abrasion resulted in a significant reduction of mTBS compared to the untreated controls (p<0.05, Tukey´s test). Between erosion (G2) and erosion in combination with abrasion (G3) no significant differences could be detected (p>0.05, Tukey´s test). Pairwise comparison of the Xeno V groups and the Futurabond NR groups also did not show any significant differences (p>0.05, Tukey´s test). Conclusion: Erosion as well as erosion in combination with abrasion highly affected the mTBS of the one-step self-etch adhesive and the two-step self-etch adhesive in vitro.